This invention relates to a novel vacuum electron device having a directly-heated matrix-cathode assembly.
A vacuum electron divice is generally comprised of an evacuated envelope and means for producing an electron emission within the envelope. One such means, referred to as a matrix or dispenser cathode, comprises a porous body or matrix of refractory metal having electron-emission material in the pores of the body. In previous assemblies, the body is supported on or in a refractory member, usually a metal sheath or container. The support member is heated to its operating temperature either indirectly by an electric current passing through a separate heater, as shown, for example in U.S. Pat. No. 3,760,218, to L. J. Cronin; or directly by an electric current passing through the support member, as shown for example, in U.S. Pat. No. 3,758,808 to W. Held et al. In U.S. Pat. No. 3,263,115 to H. H. Glascock et al, legs are attached to the support member, and the electric current passes through and heats the legs, the support member and the body. In Glascock et al, the legs, which heat the support member by conduction and radiation, are shaped to confine heat to the support member.
Such previous assemblies are bulky so that an assembly may not conveniently fit within a commercial-type television-picture tube. Due to the mass and the total radiating surface of the previous assemblies, the power efficiencies of the assemblies are less than may be desired. The power consumption may be too high to be practical for use in present-day television picture tubes. Such previous assemblies are relatively massive so that their rate of heating-up is too slow to be acceptable for use in many tube types.